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JCECE Engineering JCECE Engineering Solved Paper-2002

  • question_answer
    A tuning fork gives \[4\] beats with \[50\,\,cm\] length of a sonometer wire. If the length of the wire is shortened by \[1\,\,cm\] the number of beats is still the same. The frequency of the fork is:

    A) \[396\,\,Hz\]                     

    B)  \[400\,\,Hz\]

    C)  \[404\,\,Hz\]                    

    D)  \[384\,\,Hz\]

    Correct Answer: A

    Solution :

    According to law of length of a stretched string                 \[n\propto \frac{1}{l}\] or            \[{{n}_{1}}{{l}_{1}}={{n}_{2}}{{l}_{2}}\] Given,   \[{{n}_{1}}=n-4,\,\,{{n}_{2}}=n+4,\,\,{{l}_{1}}=50\,\,cm\]                                                                 \[{{l}_{2}}=49\,\,cm\] Hence,  \[(n-4)\times 50=(n+4)\times 49\] or            \[50n-200=49n+196\] or            \[n=396\,\,Hz\]


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